arXiv subjects

Yug Joshi

Publications and source records attributed to Yug Joshi.

5 recordsLinked to original sources

arXiv2026

Conditional spinodal decomposition in Li-Mg anodes for lithium metal batteries

The development of batteries with high energy density, short charging times and use of sustainable materials is critical for decarbonization. Magnesium (Mg)-based anodes for lithium (Li) metal batteries promote homogeneous Li plating, thereby avoiding the formation of Li dendrites that cause short circuits and battery failure. However, microstructural modifications induced by Li-alloying and their influence on battery operation remain elusive. Here, we unveil the previously unknown formation of an ordered B2 phase, which creates a conditional spinodal decomposition with the \b{eta}-body-centered cubic phase. Chemical fluctuations characteristic of spinodal decomposition give rise to uniformly dispersed Li-rich \b{eta}-BCC and Li-poor B2 continuous interconnected phases, with the former providing a fast diffusion pathway for Li diffusion towards the anode, hence decreasing the propensity for dendrite formation at elevated current density. This is achieved using Earth-abundant and inexpensive Mg.

cond-mat.mtrl-sci↗

arXiv2025

Self-supported bulk MXene electrodes for electrochemical hydrogen applications

MXenes are promising candidates for electrochemical applications due to their high conductivity, tunable surface chemistry, and catalytic potential. However, their use in bulk electrode form remains unexplored despite advantages such as higher current density and improved mechanical integrity. Herein, we present a methodology for the fabrication of self-supported vdW solid Ti3C2Tz MXene electrodes, produced by cold compaction followed by vacuum heat treatment at 600 {\deg}C, which effectively removes interlayer confined water and stabilizes the bulk 3D structure. The resulting binder-free electrodes exhibit enhanced mechanical robustness along with structural and chemical stability in various electrolytes. The MXene electrodes demonstrate adequate HER activity while maintaining electrochemical stability over time, with minimal oxidation or changes in termination surface chemistry. This approach is scalable and cost-effective, overcoming limitations of nanoscale MXene architectures in electrochemical environments and offering a practical pathway toward MXene-based materials for sustainable hydrogen energy technologies.

cond-mat.mtrl-sci↗

arXiv2025

Is Platinum a Proton Blocking Catalyst?

Platinum, to date, is the most widely applied electrocatalyst for hydrogen evolution reaction (HER) in acidic media. It is assumed to be a proton-blocking catalyst with only surface-limited adsorption of the reaction intermediates. Here, we critically evaluate the bulk interaction of Pt with hydrogen (H), and its heavier isotope deuterium (D), by monitoring operando mass change of the Pt electrode during galvanostatic heavy/water splitting by employing an electrochemical quartz crystal microbalance. Unexpectedly, we observe an irreversible temporal mass gain and a change in the reaction's overpotential, arising from diffusion of H/D into Pt, confirmed by atom probe tomography and thermal desorption spectroscopy. Sub-surface concentration of at least ca. 15 at. % of D in Pt was observed, diffusing down to a depth of more than 10 nm. Analytical description quantified the diffusion coefficient of D in Pt to be 3.2X10^-18 cm2Xs-1. These findings challenge the existing credence of Pt-proton interaction being limited to the surface, prompting the expansion of the catalyst design strategies to account for property-modifying bulk diffusion of H/D in the Pt matrix

physics.chem-ph↗

arXiv2025

Vacuum Dealloyed Brass as Li-Metal Battery Current Collector: Effect of Zinc and Porosity

"Anode-free" lithium-metal batteries promise significantly higher energy density than conventional graphite-based lithium-ion batteries; however, lithium dendrite growth can lead to internal short circuits with associated safety risks. While porous current collectors can suppress dendrite growth, optimal porosity and composition remain unknown. Here, we show that the temperature during vapor phase dealloying (VPD) of alpha-brass (Cu63Zn37) controls the surface Zn concentration, decreasing from 8 percent to below 1 percent from 500 to 800 degrees C. The surface composition is controlled by the temperature-dependent diffusion. A battery cell maintains greater than 90 percent Coulombic efficiency (CE) over 100 cycles when the Zn content is the lowest, whereas the higher-Zn samples degraded to approximately 70 percent CE. The difference in surface composition has hence dramatic effects on battery performance, and our results demonstrate how precise compositional control enables stable lithium-metal battery operation, establishing about 1 atomic percent surface Zn as optimal for preventing capacity fading and uniform lithium plating, while establishing predictive relationships between processing temperature and surface composition. This work provides design rules for multifunctional current collectors and demonstrates scalable VPD production for next-generation batteries.

cond-mat.mtrl-sci↗

arXiv2025

Electrochemically-driven formation of Intermetallic Cu3ZnLi2 alters Li-transport in nanostructured bimetallic battery anode

The role of Li-based batteries in the electrification of society cannot be understated, however their operational lifetime is often limited by the formation of dendrites, i.e. the localised deposition of Li that can cause shorts between the two electrodes leading to the failure of the battery. Nanocrystalline bimetallic current collectors can be used for anode-free Li-metal batteries, with improved Li plating and limited or suppressed formation of dendrites. Here, we demonstrate that the microstructure of an alpha-Brass current collector, Cu 63% Zn 37%, used in an anode-free Li-metal battery evolves during cycling. It initially had a nanocrystalline deformation layer approximately 80 nm in thickness after polishing. After 100 cycles, the initial deformed brass layer was partially converted to a ternary Laves phase Cu3ZnLi2 within a nanocrystalline brass matrix that grew to 200 - 250 nm in thickness. Upon Li stripping, the phase partially decomposes electrochemically, but what remains can sequester Li thus forming "dead Li" thereby contributing to capacity loss. We propose a mechanism for the microstructural evolution including dynamic recrystallization and phase formation. Since this ternary Laves phase emerges during electrochemical cycling alone, binary alloy current collectors must be assessed for metastable ternary phase formation under different cycling conditions to either stabilize and exploit such phases or electrochemically fully strip them.

cond-mat.mtrl-sci↗